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Circuit Description
Low Current Base Tech 3.5
EXCITER UNIT
1) VCO
Section
The oscillator circuit generates transmitter frequency. Then this signal is fed to the 3-stage of amplifier,
buffer amplifier Q302, pre-amplifier IC301 and post amplifier Q303 and lead to the final amplifier, and
lead to the final amplifier.
2) PLL
section
Basically, the circuit description is the same as RX. The PLL IC inclusive with prescaler (IC208)
compares the phase between VCO signal and reference oscillator frequency (12.00 MHz) by method of
dividing the frequency, and produces VCO control signal. Then this VCO control signal is fed to the
charge pump, and fed to the low-pass-filter. The supply voltage of charge pump is amplified by IC210
(to approx. 13 V) to achieve greater S/N ratio.
3) Modulation
Section
The modulation signal is fed to both VCO and the reference oscillator (TCVXO 12.00 MHz), this permits
very flat modulation characteristics against low frequency (DC). This is an advantage when BASE
TECH III is used as a POCSAG transmitter.
4) TX Exciter Section
The VCO signal is amplified by Q211 to achieve 80 mW.
5) Low
Current
Improvements
An additional 5.5 volt dc source has replaced the 12 V dc source for main on board power. An additional
12 volt line has been added for the 7 V dc regulator. This significantly reduces current consumption
losses to heat.
POWER AMPLIFIER
1) Power Amplifier (VHF = 5-110W/ UHF = 2-100W)
The 80 mW signal from TX Exciter stage is fed to PM501 to produce 10W output. Then, Q504 and Q505
amplify to 110/100W. This signal is fed to the Low-Pass- Filter to eliminate the harmonics and spurious
frequencies. An APC circuit formed by IC502 stabilizes the output power at the set level. An IC501
protects final stage transistors from the reverse power caused by a mismatched antenna system
2) Power Amplifier (VHF = 60W / UHF = 50W)
The 80 mW signal is fed to PM501 to achieve 60/50W output power. Then, signal is fed to the LPF to
eliminate the harmonics spurious frequencies. An APC circuit formed by IC502, IC503, Q504 and
Q505 stabilizes the output power at the set level. IC501 protects PM501 from the reverse power
caused by a mismatched antenna system
© 2012 Midland Radio Corporation
14
Содержание 91-1060-91-1110
Страница 22: ...Circuit Description Low Current Base Tech 3 5 Notes 2012 Midland Radio Corporation 18 ...
Страница 23: ...Block Diagram VHF 60 Watt Low Current Base Tech 3 5 19 2012 Midland Radio Corporation ...
Страница 24: ...Block Diagram VHF 110 Watt Low Current Base Tech 3 5 2012 Midland Radio Corporation 20 ...
Страница 25: ...Block Diagram UHF 50 Watt Low Current Base Tech 3 5 21 2012 Midland Radio Corporation ...
Страница 26: ...Block Diagram UHF 100 Watt Low Current Base Tech 3 5 2012 Midland Radio Corporation 22 ...
Страница 27: ...Front Panel Unit Schematic Low Current Base Tech 3 5 23 2012 Midland Radio Corporation ...
Страница 28: ...Analog Logic Unit Schematic Low Current Base Tech 3 5 2012 Midland Radio Corporation 24 ...
Страница 29: ...VHF RX Main Unit Schematic Low Current Base Tech 3 5 25 2012 Midland Radio Corporation ...
Страница 30: ...VHF RX VCO Unit Schematic Low Current Base Tech 3 5 2012 Midland Radio Corporation 26 ...
Страница 31: ...VHF TX Main Unit Schematic Low Current Base Tech 3 5 27 2012 Midland Radio Corporation ...
Страница 32: ...UHF RX Main Unit Schematic Low Current Base Tech 3 5 2012 Midland Radio Corporation 28 ...
Страница 33: ...UHF RX VCO Unit Schematic Low Current Base Tech 3 5 29 2012 Midland Radio Corporation ...
Страница 34: ...UHF TX Main Unit Schematic Low Current Base Tech 3 5 2012 Midland Radio Corporation 30 ...
Страница 35: ...Front Panel Unit Layouts Low Current Base Tech 3 5 31 2012 Midland Radio Corporation ...
Страница 36: ...Analog Logic Unit Layouts Low Current Base Tech 3 5 2012 Midland Radio Corporation 32 ...
Страница 42: ...THIS PAGE INTENTIONALLY LEFT BLANK 2012 Midland Radio Corporation 38 ...
Страница 43: ...Palm Microphone Schematic Low Current Base Tech 3 5 39 2012 Midland Radio Corporation ...
Страница 62: ...5900 PARRETTA DRIVE KANSAS CITY MISSOURI 64120 PHONE 816 241 8500 FAX 816 241 5713 www midlandradio com ...